树莓派 ubuntu-mate系统换源

网上有很多教程，在更换之后update的时候会报404的错误，导致后续装包的时候找不到资源

1. 换源

   sudo vim /etc/apt/sources.list

   # 将一下内容粘贴到sources.list中
   deb http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic main restricted universe multiverse
   deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic main restricted universe multiverse
   
   deb http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-updates main restricted universe multiverse
   deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-updates main restricted universe multiverse
   
   deb http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-security main restricted universe multiverse
   deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-security main restricted universe multiverse
   
   deb http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-backports main restricted universe multiverse
   deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-backports main restricted universe multiverse
   

   wq保存退出

2. 更新
   sudo apt-get update
   sudo apt-get upgrade